The overall air transportation sector is currently under significant stress. With the demand in aircraft operations expected at least to double by the 2025 timeframe, there are well-founded concerns that current air transportation systems will not be able to accommodate this growth. Existing systems are unable to process and provide flight information in real time, and current processes and procedures do not provide the flexibility needed to meet the growing demand. New security requirements are affecting the ability to efficiently move people and cargo. In addition, the growth in air transportation has provoked community concerns over aircraft noise,air quality.and airspace congestion. In summary, with the tools and procedures in use today, the effective increase of air traffic will be fundamentally limited and it is already approaching its limits. Focusing on communications related aspects, the following high-level requirements can be identified, in order to allow future systems to be compatible with the expected air-traffic increase:

Pilots situation awareness shall be improved

Capacity at airports, today one of the main limiting structural factors, shall be increased

To cope with these issues, new communication concepts are being developed in SESAR and in the AOC/APC domains. They aim at the definition of an access to an open system.This results in a collection of communications technologies targeted at specific operational settings. This represents a considerable extra burden to be carried by the aircraft, should the new radio links be implemented in stand-alone equipments. Moreover, although it has been suggested that the new systems will eventually replace the legacy communications systems, the likelihood is that there will be a lengthy period where aircraft will be fitted with all of the systems for global interoperability.This is the forecast expressed by SESAR, and the additional airborne equipment required during this transition phase severely threatens the realization of the future communications vision. Hence, a different approach aiming at a broader level of integration is needed to achieve the required increase of capacity, safety, security and efficiency of air transportation operations while at the same time keeping complexity and cost of on-board networks and equipments within a sustainable level.